Electronic temperature

A non-tliennal, non-equilibrium plasma is characterized by an electron temperature much larger tlian tire ion temperature and tire neutral gas temperature (T T. Typical non-tliennal, non-equilibrium plasmas... 

Central to the categorization of plasmas are electron temperature and electron density. Electrons have a distribution of energies, so it is useful to assume a MaxweUian distribution, in terms of electron energy, E, such that... 

Plasma Types. Eigure 1 (7—9) indicates the various types of plasmas according to their electron density and electron temperature. The colder or low electron energy regions contain cold plasmas such as interstellar and interplanetary space the earth s ionosphere, of which the aurora boreaUs would be a visible type alkaU-vapor plasmas some flames and condensed-state plasmas, including semiconductors (qv). 

Fig. 1. Electron temperature and density regions for plasmas (7—9) where the numbers and the diagonal lines represent (—) the Debye screening length,...

Controlled thermonuclear fusion experiments and certain types of confined arcs known as pinches have temperatures in the 5 x 10 -10 K range. However, to be successhil, controlled thermonuclear fusion needs to take place from 6 x 10 -10 K. In fact, the goal of all fusion devices is to produce high ion temperatures in excess of the electron temperature (10). 

Electrodes or Langmuir probes may be inserted into plasmas that are large enough (>1 cm) and relatively cool (<10 K). The net current to the probe is measured as a function of the appHed voltage. Electron temperatures, electron and ion densities, and space and wall potentials may be derived from the probe signals. Interaction of plasmas with soHd probes tends to perturb plasma conditions. 

Processing variables that affect the properties of the thermal CVD material include the precursor vapors being used, substrate temperature, precursor vapor temperature gradient above substrate, gas flow pattern and velocity, gas composition and pressure, vapor saturation above substrate, diffusion rate through the boundary layer, substrate material, and impurities in the gases. Eor PECVD, plasma uniformity, plasma properties such as ion and electron temperature and densities, and concurrent energetic particle bombardment during deposition are also important. 

Quantum well interface roughness Carrier or doping density Electron temperature Rotational relaxation times Viscosity Relative quantity Molecular weight Polymer conformation Radiative efficiency Surface damage Excited state lifetime Impurity or defect concentration... 

Answer An electronic temperature monitor could be equipped with a bar-code liquid crystal display which could be read by a portable bar-code reader. These devices have a memory so several readings may be taken before they are readout over a telephone modem to a data logging computer. The simplest way to read the acid type would be to post a label that is bar-coded to indicate the acid type. Tire acid quantity could be indicated by an acid level gage using a bar-code display of the level. The aluminum quality could be indicated by displaying a label in bar-code. The amount of aluminum could be determined by weight using a bar-code readout on the scales. 

The heavier ions with their much greater inertia cannot respond to the rapid changes in field direction. As a result, their temperature and that of the plasma remain low, as opposed to the electron temperature (hence the name non-isothermal plasma). 

Figure 12. Variation of the plasma parameters of a CH4/H2 plasma with pressure, (a) Plasma potential, (b) Electron temperature, (c) Electron density. Reprinted with permission from [88], K. Okada et al., /. Vac. Sci. TechnoL, A 17, 721 (1999). 1999, American Institute of Physics.

Figure 14. Variation of the plasma parameters of a CH4/CO/H2 plasma with [CO] content, (a) Plasma potential, (b) Electron temperature, (c) Electron density.

In general, the substrate temperature will remain unchanged, while pressure, power, and gas flow rates have to be adjusted so that the plasma chemistry is not affected significantly. Grill [117] conceptualizes plasma processing as two consecutive processes the formation of reactive species, and the mass transport of these species to surfaces to be processed. If the dissociation of precursor molecules can be described by a single electron collision process, the electron impact reaction rates depend only on the ratio of electric field to pressure, E/p, because the electron temperature is determined mainly by this ratio. 

The fluid model is a description of the RF discharge in terms of averaged quantities [268, 269]. Balance equations for particle, momentum, and/or energy density are solved consistently with the Poisson equation for the electric field. Fluxes described by drift and diffusion terms may replace the momentum balance. In most cases, for the electrons both the particle density and the energy are incorporated, whereas for the ions only the densities are calculated. If the balance equation for the averaged electron energy is incorporated, the electron transport coefficients and the ionization, attachment, and excitation rates can be handled as functions of the electron temperature instead of the local electric field. 

Subsequently, because the electron temperature is known as a function of the electric field E, the temperature Te can be used instead of as a parameter for coefficients and rates, by elimination of E. Thus, the coefficients are available both as a function of E and of Te. Both the loeal electrie field [225, 269] and the electron temperature [239,268] have been used as parameters in fluid modeling. 

Methods that compensate for nonequilibrium effects in the situation of E-parametrized coefficients are very complicated, and are sometimes not firmly grounded. Because the electron temperature also gives reasonable results without correction methods, the rate and transport coefficients were implemented as a function of the electron energy, as obtained from the PIC calculations presented in Figure 25. 

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